Spectacle ophthalmic lenses are worn and widely used for correcting many different types of vision deficiencies. These include defects such as near-sightedness (myopia) and far-sightedness (hypermetropia), astigmatism, and defects in near-range vision usually associated with aging (presbyopia).
Ophthalmologists or optometrists routinely improve the visual acuity of a wearer by correcting refractive errors of his eyes in terms of sphere (SPH), cylinder (CYL) and cylinder axis (AXE). Near vision zone addition power (ADD) is also prescribed when the wearer is presbyotic. Other data may be prescribed, in particular a prism in certain specific cases.
A lens design, in this document, is what characterises an ophthalmic product. The wording “ophthalmic product” refers to a lens family for all prescriptions where all the lenses of the lens family have common features.
In the frame of the present invention a “design” of a spectacle ophthalmic lens has to be understood as the features of the optical system of said lens which are not directly determined by the wearer standard prescription parameters consisting of sphere, cylinder, cylinder axis and power addition values determined for said wearer.
In other words, a “design” is a widely used wording known from the man skilled in the art to designate the set of parameters, except here above mentioned wearer standard prescription parameters, allowing defining an optical function of a generic optical system; each ophthalmic lens manufacturer has its own designs, particularly for aspherical lenses and for progressive addition lenses (PAL). As for an example, a PAL “design” results of an optimization of the progressive surface so as to restore a presbyope's ability to see clearly at all distances but also to optimally respect all physiological visual functions such as foveal vision, extra-foveal vision, binocular vision and to minimize unwanted astigmatisms. PAL “designs” are tested through rigorous clinical trials before being commercialized.
Ophthalmic lens manufacturers do continuously improve the optical performances of their lens designs.
According to current trends, designs may also be suitable to take into account a number of design particularities, including for example personalization parameters.
The resulting optical features of an ophthalmic lens design within given prescription ranges are not easy to determine because numerous parameters have to be taken into account. Furthermore, it is also difficult to compare on a reliable way different ophthalmic lens designs within given prescription ranges. Said optical features determinations or design comparisons are done, up to now, on a point by point basis where only some characteristic points of a lens and a very limited number of prescription data are chosen.